The present invention relates to a vehicle theft prevention device, and in particular to a vehicle theft prevention device which prohibits release of a theft prevention function under a certain condition even when the release is instructed using an authorized portable tool.
Generally, a vehicle door may be provided with a locking device which can be unlocked only using an authorized portable tool (such as a key). Also, an engine can generally be activated only using an authorized ignition key. These are conventional vehicle protections against theft. However, in the case of a mechanical locking device, the device may be removed or broken, as a result of which the vehicle is made drivable and could be stolen. The more malicious vehicle thefts have become lately, the more reliable vehicle theft prevention devices are desirably equipped on a vehicle.
To meet this demand, a vehicle with an additional electronic locking device has been introduced to the market. An electronic locking device, called, e.g., an immobilizer, incorporates a transponder sending an encryption code to an ignition key. The transponder, empowered by electronic waves received via an antenna provided to a key cylinder, sends an encryption code stored therein. An immobilizer ECU is connected to the antenna and determines whether or not the encryption code from the transponder is correct. The immobilizer ECU, also connected to an engine ECU for controlling ignition of and fuel supply to an engine, informs the engine ECU of whether or not a correct encryption code is obtained. With no correct encryption code received by the immobilizer ECU, the engine ECU prohibits fuel supply to and ignition of the engine whereby the engine and the vehicle can be prevented from being activated and therefore running, respectively, in an attempt to activate the vehicle without using an authorized key.
However, in the case of an immobilizer-mounted vehicle, this arrangement, although it can prevent stealing of a vehicle alone, cannot prevent stealing of a vehicle together with a tool (such as an ignition key) for sending an encryption code to the immobilizer, resultantly leaving the vehicle free from any measure against a vehicle theft.
Also, if a spare key should be stolen, as two or more spare keys are generally available to a vehicle, even though they may not usually be in use, the above arrangement leaves a vehicle free from any protection against vehicle theft.
The present invention has been conceived to overcome the above problems, and aims to provide a vehicle theft prevention device for prohibiting release of a theft prevention function under a certain condition even when a regular authorized is used to instruct the release, to thereby prevent the vehicle from running.
In order to achieve the above object, according to a first aspect of the present invention, there is provided
a vehicle theft prevention device including code obtaining means for obtaining, from a portable tool, a request code for requesting release of vehicle theft prevention control, memory means for storing a specific code allowing the release, control means for comparing the request code obtained and the specific code so as to release the vehicle theft prevention control when the request code obtained coincides with the specific code, and to maintain the vehicle theft prevention control when they do not coincide. The vehicle theft prevention device comprises code changing means for changing specific codes at a predetermined changing timing so that a currently effective specific code is invalidated so as to disagree with a request code from the portable tool.
Here, vehicle theft prevention control refers to control over vehicle theft prevention functions, including door lock control, steering lock control, and engine activation prohibition control. A currently effective specific code refers to, for example, a code at a certain timing corresponding to a request code obtained from an authorized portable tool and so on (including ones incorporated into an ignition key, and so on), and capable of releasing the theft prevention control. A predetermined changing timing refers to a timing determined in advance by an authorized user or dealer of the vehicle or a timing at which an authorized user applies a change operation.
With the above arrangement, even when a request code corresponding to a specific code capable of releasing the vehicle theft prevention control at a certain timing is supplied using a portable tool, that specific code may be invalidated at a different timing. Therefore, without the knowledge of means for providing a request code corresponding to a new specific code or possession of a portable tool providing such a request code, a party other than an authorized user or dealer cannot release the theft prevention control as the control means of the vehicle prohibits release of the theft prevention control. As a result, vehicle theft can be reliably prevented.
According to a second aspect of the present invention, in the first aspect,
the memory means has a plurality of predetermined specific codes, and the code changing means sequentially selects the plurality of predetermined specific codes at a predetermined changing timing to determine a next specific code.
A next specific code refers to a specific code after specific code change, which corresponds to a reserved portable tool and so on.
With this arrangement, as specific codes are periodically changed, request condition for a request code becomes more severe. As a result, reliability of a theft prevention function can be improved. Note that intervals for selection of a specific code may or may not be constant.
According to a third aspect of the present invention, in the first or second aspect, timing to active the code changing means is determined based on an accumulated value of a vehicle running distance.
According to a fourth aspect of the present invention, in the first or second aspect, timing to active the code changing means is determined based on an accumulated time after change of the specific codes.
With this arrangement, a user with low driving-frequency can be prevented from excessive changing of a specific code, thereby being subjected to reduced burden of changing portable tools every time the vehicle is used. Also, in the case where a vehicle is stolen together with a portable tool capable of providing a request code for releasing vehicle theft prevention control at a certain timing, the owner of the stolen vehicle can be kept safely away from the thief as the stolen vehicle remains drivable within a certain distance or time period. In addition, as the stolen vehicle will be made no longer drivable after running a predetermined distance or a predetermined time, subsequent searching for the stolen vehicle can be facilitated.
According to a fifth aspect of the present invention, in any of first through fourth aspects, timing to activate the code changing means can be changed as desired.
With this arrangement, the changing timing can be set according to the perceived level of safety of an area where the vehicle is mainly used or usually parked. This allows the user to apply theft prevention measure as they desire.
According to a sixth aspect of the present invention, in any of the first to fifth aspects, the control means requests comparison using a corresponding request code when specific codes are changed by the code changing means, irrespective of a state of vehicle control, so as to maintain operation thereof.
With this arrangement, after the change of specific codes, a request code corresponding to a new specific code is compared with the new specific code even though the vehicle is in a state allowing release of theft prevention control, e.g., in a running state. When they do not coincide with each other, it is possible to stop the vehicle. Therefore, with this arrangement, a use of a stolen vehicle can be reliably prohibited. Note that, desirably, the control means starts the operation in response to confirmation that an engine is stopped or a parking brake is placed in an ON position as it is not preferable to apply an engine stop operation and so on (prohibition of restarting) to a running vehicle.
According to a seventh aspect of the present invention, a vehicle theft prevention device in any of second to sixth aspects, comprises control limit means for limiting a vehicle theft prevention function allowed based on a specific code having a low frequency of coincidence with a request code obtained, the specific code being among those selected by the code changing means.
A specific code with a low frequency of coincidence refers to a code sent from a back-up portable tool, and so on, which, for example, may be kept for a long time in a place different from where the vehicle is used, and resultantly kept away from comparison with a request code for more than a predetermined time (e.g., 500 hours). Limiting a vehicle theft prevention function means partial or complete prohibition of release of the theft prevention control.
With this arrangement, a portable tool with low frequency of use is made substantially incapable of controlling the vehicle. Therefore, should a back-up portable tool and so on be stolen, illegal use of the stolen vehicle can be prevented. be stolen, illegal use of the stolen vehicle can be prevented.
According to an eighth aspect of the present invention, in any of the first to seventh aspects, canceling means is also included for canceling invalidation of a specific code, under specific conditions.
According to an eighth aspect of the present invention, in any of the first to seventh aspects, canceling means is also included for canceling invalidation of a specific code, under specific conditions.
Here, to cancel invalidation of a specific code means temporary release of an operation of a theft prevention device by invalidating a specific code, or postponing of shifting to a state where a specific code is invalidated.
With this arrangement, as anyone who meets a predetermined condition, i.e., an authorized user or dealer, and so on, can temporarily release invalidation of a specific code and postpone shifting to a state where a specific code is invalidated, it is possible to prevent deterioration of the ease with which the user can use the vehicle theft prevention device, while maintaining the theft preventing effect.
According to a ninth aspect, in the eighth aspect, the canceling means operates when a predetermined condition is met by a predetermined manual canceling operating.
Here, a predetermined manual canceling operation is an operation for inputting a code number or combining switches of various devices equipped in the vehicle.
With this arrangement, only a specific person who can know the manual canceling operation (an authorized user or dealer, and so on) can easily cancel invalidation of a specific code.
According to a tenth aspect, in the eighth aspect, the canceling means operates when a canceling request code stored in the memory means is obtained.
According to an eleventh aspect, in the tenth aspect, the canceling request code is sent from a portable tool other than a portable tool which sends the request code.
With this arrangement, only a specific person who can know the manual canceling operation (an authorized user or dealer, and so on) can easily cancel invalidation of a specific code.